The present application relates to metal casting, and more particularly, but not exclusively, relates to the continuous casting of metal slabs and cooling control thereof.
Typical continuous casting arrangements include a water-cooled mold that provides initial/primary cooling of the molten metal being cast. Robust and accurate control of secondary cooling, such as water spray cooling, with such arrangements is often desired for successful operation and the production of high quality products. Secondary cooling is often a focus of thin slab casters because high casting speed and a tight machine radius typically require carefully-prescribed temperature profiles to avoid various problems, such as cracks and “whale formation”. Indeed, cracking can be reduced by successful control of the secondary cooling to maintain these optimal temperature profiles through changes in casting process conditions. Whale formation can be avoided by ensuring that the metallurgical length (maximum length of the liquid core of the continuous-cast metal) is always less than the length of that portion of the caster where support rolls contain the strand to prevent excessive bulging.
Secondary cooling presents several challenges to control. Conventional feedback control systems based on hardware sensors are typically unsuccessful because emissivity variations from intermittent surface scale and the harsh environment of the steam-filled spray chamber makes optical pyrometers unreliable. Secondary cooling of thin-slab casting is particularly difficult to control because of the thinner shell, the higher casting speed, and the increased relevance of solidification in the mold, which is not easy to predict accurately. Thus, there is a need for further contributions in this area of technology.